Solid-state NMR with dynamic nuclear polarization (DNP-NMR) has recently attracted attention as a highly sensitive NMR measurement method for analyzing polymers. We recently investigated DNP-NMR for insoluble polymers, particularly cross-linked polymers, engineering plastics, and polymer-supported catalysts, and achieved high NMR signal sensitivity at a routinely accessible level. In this focus review, we present case studies on DNP-NMR measurements for a wide range of polymers.

This study examined how changing the water-glycerol solvent composition affects the self-healing and viscoelastic properties of self-healing gels, which have host-guest inclusion complexes as reversible crosslinks. Increasing glycerol concentration in the mixture solvent reduced hydrophobic interactions between β-cyclodextrin and adamantane, lowering the association constant of host-guest inclusion complexes. The weakened hydrophobic interaction hinders complex recombination and enhances the mobility of the network chains. Consequently, the enhancement of mobility improved the healing ratio because the interfacial diffusion of the chains was promoted at the repair interfaces.

Alternating π-conjugated copolymers containing 9,9-dialkylfluorene (Fl) units have been widely studied, but there are few of these copolymers with sp²-carbon functionalized Fl units. In this study, we expand this limitation by performing the anodic chlorination of alternating π-conjugated copolymers, which are composed of Fl and another arylene (Ar) (P(Fl-Ar)s), using an acetonitrile solution that contains aluminum chloride as an electrolyte. The sp²-carbon at the fluorene ring was successfully chlorinated by anodic chlorination. P(Fl-Ar)s containing sp²-chlorinated fluorene units has different emission properties from the original P(Fl-Ar)s.

The peptide-Au nanoparticle (AuNP)-TiO₂ nanocomposite in which AuNPs were connected by TiO₂-coated conductive peptide nanowire was acted as effective VOC sensor.

Functional dyes offer fascinating properties in response to external stimuli and enable unique stimuli-responsive functions in materials by chemical incorporation into polymers. In this review, we highlight our recent studies conducted in the last half decade on stimuli-responsive smart polymers and polymeric materials offering, for example, switchable adhesion, mechanical actuation, and chemical sensing based on functional dyes that are chemically incorporated into the structures, with a particular focus on the stimuli of light, force, electric fields, and chemicals including water.

The degree of gel-gel phase separation (GGPS) was compared using multi-arm poly(ethylene glycol) (PEG) hydrogels. GGPS can occur at c < c*, with 8-arm PEG exhibiting a stronger turbidity (D) indicating stronger GGPS compared to 4-arm PEG. This indicates that phase-separated PEG can be obtained at low concentrations simply by increasing the number of branches. Furthermore, phase-separated 8-arm PEG showed higher osteogenic differentiation in vitro.

Sodium alginate and carboxymethyl chitosan were used as raw materials, and the dynamic imine bonding network formed by the two was combined with the coordination bonding network formed by acrylic acid and aluminum ions. The dual-network structure of the hydrogel not only gives the hydrogel excellent self-healing properties, but also gives the hydrogel excellent mechanical properties, with a strain at break as high as 3787%. In addition, the hydrogel has the antibacterial property of inhibiting the growth of E. coli and S. aureus and good electrical conductivity.

Heat insulators are key materials for efficient energy use and reduction of CO₂ emissions. Recently, we examined cross-linked polymethylsilsesquioxane (MSQ) for use as the basic structure of heat-resistant insulation materials. In this study, we prepared MSQs with different cross-linking units and examined the effects of their structures on the heat resistance and heat insulation properties. Among those, MSQ linked by diethynylbenzene had sufficiently low thermal diffusivity and moderately high heat resistance.

In this study, branched polymers with different copolymerization composition ratios of α-chloro-ε-caprolactone (α-ClCL) and ε-caprolactone (ε-CL) were prepared using α-ClCL and trimethylolpropane as the initiator. Furthermore, acryloyl groups were introduced at each chain ends of branched polymer to form macromonomers capable of cross-linking reactions. Films obtained by photo-crosslinking macromonomers with chloro groups showed shape-memory properties. In addition, the chloro group introduced by α-ClCL was converted into an azide group. This film is expected to be applied to various functional surfaces through the click reaction in the future.